I doubt that any real kb techs monitor this forum, but here goes:

I changed the key contacts in my PA900, and after reassembling it, putting in the MANY, many screws, and figuring out how to make sure the keys don't bounce (there's a very specific way to reinsert the circuit board after you deal with the contacts), I powered it up to find ... a very strange anomaly. The bottom 2/3 of the keys function as they should, but starting at the top and going down, every 4th key will not sound. It's a cyclical pattern that repeats for more than an octave.
Can anyone think of a mechanical reason why this would occur? The contact strips come in lengths of 12 (and one of 13), so that kind of rules out any one strip as a target for my attention. The 1 in 4 dead key issue is a real brain tease.

I updated the OS, reinstalled the resources, and did everything I could think of to overcome a software issue. I have a sneaky suspicion that there's a loose wire, or ribbon, or "something" that I didn't connect correctly ... although I was pretty thorough as I unplugged and re plugged those things.

I'm baffled, and open to educated suggestions.

Dave can you call Korg service and see what they think?

Best to try to get help on the Korg Forums. Probably PA4 Forum has the most readers.
http://www.korgforums.com/forum/phpBB2/viewforum.php?f=76

After talking with Fran, I ruled out a motherboard issue. The sounds and features all work, EXCEPT those few keys I mentioned. This is most likely a short, or crack in the circuit board. MIDI works as it should, as do the recorder, players, rhythms and sounds. "SOMETHING" in the keybed, or connections has failed.

I retired the unit to sit atop my Rhodes and serve as a sound source, a monitor amp/speakers, a quick MP3 recorder, and general cool stack topper.

How's it look?
(The kb stuffed in the middle is a Korg i5s that I got from Boo. It serves as a controller for the 900, so I don't have to reach) I play bass lines, and accent sounds on that, while I comp on the Rhodes. Like the old days

Did you try disconnecting the connector cable and reconnecting it. I would try that. Can't hurt. It sounds like a connection problem. Are you sure you connected all the connectors. Not criticizing your skills, just sometimes it is easy to miss a cable when taking things apart. Best of luck to you.

As far as I know, and I was very careful to count ... I connected all cables that I disconnected. I did this whole thing 3 times ... same result. My best guess is a damaged circuit board. maybe I screwed it in too tight, maybe a flash of static electricity found it's way in ...who knows? As for now - I'm happy where it is. Someday I may open it up again, but it serves a purpose as it is. Sooooooo many screws. Who's got that kinda time?

In addition to cable connectors, there is one other vulnerability that we often overlook. I had an intermittent problem with my organ (KeyB) that was driving me crazy. Description of the problem is unimportant but it was obviously electronic. I described the problem over on the Keyboard Corners forum and someone suggested that I RESEAT the 4 main circuit boards (one for each set of drawbars). Despite a lot of skepticism on my part, I tried it. Three of the four could be seated more firmly into the motherboard. After reseating and closing up, I turned it on and Voila!, no more problems. That was two years ago and I have not had even a hint of a problem since (and I play it daily - extensively). Yeah, yeah, I know....the screws, but it might be worth a try.

chas

The circuit board that controls the keys is a two piece design that's held together with aluminum type tape, or something like it. It's VERY possible that it's not seated perfectly. With the multiple connect - disconnect dance I performed, it's very likely that the board has been put back in a slightly "off" position. Good thinking. Not excited to take it apart again anytime soon, but .... maybe someday. Thanks!